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2.If the diagonal mirror is not centered within the circle formed by the bottom edge of the focuser drawtube, rotate the diagonal mirror holder about its support bolt. When the mirror is centered, tighten the lock nuts (7, Fig. 3) on the long bolt against the central hub of the
3.If the reflection of the main mirror is not centered on the surface of the diagonal mirror, adjust the 3 tilt screws (6, Fig. 3) on the back of the diagonal mirror holder to achieve correct centering.
4.You will notice three socket headed bolts on the bottom end of the telescope (5, Fig. 1) (These will be wing nuts on the
5.If the reflection of your eye is not centered within the reflection of the primary mirror, adjust the three collimation screws. Proceed by “trial and error” until you develop a feel for which screw to turn in order to change the image in any given way.
6.For final adjustments, perform a test using an actual star to confirm the accuracy of Steps 1 through 5, above. Using the 25mm eyepiece, point the telescope at a moderately bright (second or third magnitude) star, and center the image in the telescope’s field of view.
Figure 4A | Figure 4B |
7.Bring the star’s image slowly in and out of focus until you see several circles (“diffraction rings”) surrounding the star’s central disk. If Step 5 was done accurately, you will see concentric circles as in Figure 4B. An improperly collimated instrument will reveal oblong or elongated circles as in Figure 4A. Slowly adjust the three collimation screws on the mirror cell until the circles are concentric on either side of focus.
F. TIPS ON USING A DOBSONIAN TELESCOPE
1.Never lubricate the Teflon pads on the Ground Plate and Side Bearing Cradle, or the Side Bearings themselves. The Meade Starfinder Dobsonian has been designed with some inherent friction. You want the telescope to move easily when you position it, but you also want it to stay in place when you don’t. Using any kind of oil, silicone spray, wax, or grease will ruin the performance by causing the telescope to move too easily. Just keep these bearing surfaces clean; that’s all the maintenance required.
2.You will notice that your telescope will move in altitude by raising and lowering the tube, and in azimuth by rotating the base. As you observe objects in the night sky they will appear to drift out of the field of view due to the Earth’s rotation. To keep an object centered in the field of view, just lightly nudge the telescope in the proper direction. This may take a little practice at first, but you’ll soon get the hang of it.
